Method of making low density water resisting fibrous products



Patented Oct. 28, 1941 METHOD OF MAKING LOW DENSITY WATER -RESISTINGFIBROUS PRODUCTS John 0. Burton, International Falls, Minn., as-

signor, by mesne assignments, to Minnesota and Ontario Paper Company, acorporation of Minnesota No Drawing.

Application March 20, 1939,

Serial No. 263,066

4 Claims.

This invention relates to improved structural fibrous material and to aprocess for producing the structural insulating material.

An object of the invention is to produce a fibrous material which islight and porous'and has improved heat and sound insulating properties.The term structural units as used throughout the specification andclaims relates to blocks, boards, sheets or other desirable forms ofmaterial suitable for the formation, covering or lining of walls,floors, buildings, containers, or other structures where it is desirablethat they be resistant to either heat or sound or sound absorbing.

A further object of the invention is to produce porous structural unitsfrom materials consisting primarily of pulp or fibers, such as woodpulp, cor'n stalks, bagasse, jute, flax, peat or other fiber cellulosematerial, or asbestos fibers, hair, rock wool or similar inorganicfibrous materials alone or in combination with lignocellulose fibers.

It has been discovered that highly porous fibrous structures may beproduced by incorporating into a pulp or fiber mass an amount of wasteliquor resulting from Ckil'lg cellulosecontaining materials, such aswood, bagasse, corn stalks, etc. and aerating the mixture.

In practice of the invention, there is prepared a pulp composed offibers of substantially uni-- form degree of fineness (and ofsubstantially uniform size). The pulp is mixed with sufficient amount ofwater or other liquid to render the pulp sufliciently fluid forsatisfactory handling. To the pulp mass thus formed, there isincorporated waste liquor resulting from cooking lignocellulosematerial, for example synthetic-lumber black liquor, kraft black liquor,sulphite waste liquor, soda liquor, etc. The pulp mass and waste liquorare thoroughly aerated and then formed into the desired shape and dried.Drying may take place at any suitable temperature but the best resultsare obtained when using a drying temperature of about 300 to 350 F. orhigher; 7

It is to be understood that any waste or other liquor resulting fromcooking ligno-cellulose material may be used. Waste liquor as usedthroughout specification and claims means liquor resulting from cookingligno-cellulose material.

When producing semi-chemical pulp there results in what may be termedblack liquor waste which contains about to 20% of the original thecellulose material is satisfactory as a frothmaterial of theligno-cellulose material cooked.

chiefly resins, sugars and degradation products of lignin and cellulose.

When using waste liquor resulting from producing semi-chemical pulp, thefollowing process may be used to obtain highly porous and lightstructural units.

The fibers are suspended in water at a consistency of about 1 to 3%, andare placed in an aerating apparatus to which is added waste liquor in aratio of liquor to fibers of about 30:1 to 4:1, depending upon whether adensity of from about .75 to about 5 pounds per cubic foot is desired.It is preferred and generally deemed necessary that if the waste liquoris alkaline that a suitable acid or acid reacting salt be added whichresults in stiffening and stabilizing the frothy mass resulting fromaerating. The mixture is thoroughly agitated resulting in the formationof a frothy mass containing relatively small bubbles. The frothy mass isthen passed to a suitable forming device and thereafter passed to asuitable dryer.

When using kraft black Waste liquor which contains 40 to of the originalmaterial in the lignocellulose material, it is preferred that the wasteliquor be diluted to about a Baum of 5. The best results have beenobtained by varying the ratio of liquor to fibers from 15:1 to 1:1 inorder to obtain a density in the finished structural unit of from about1 to about 5 pounds per cubic foot. It is necessary when using kraftblack waste liquor to add thereto some acid to obtain a stiff and stablefroth. In general it may be stated that any acid or acid reacting saltcapable of lowering the pH between 4.0 to 6.0 will serve as a frothstabilizer. This relates particularly to synthetic lumber black liquor,kraft black liquor,.and glue. It may be stated generally that anymaterial which reduces solubility of stabilizer, and the amountof suchmaterial which should be used is the amount which will reduce thecolloidal components to their minimum solubility.

Waste liquor resulting from acid cooking (sulphite or the like) ofligno-cellulose material usually contains about 40% to about 50% theoriginal ligno cellulose material. 'It is preferred to dilutewaste-sulphite liquor to a Baum of about 4. This waste liquor when mixedwith pulpy material and thoroughly agitated, produces a froth which isfairly stable.

It is believed that the bulk of the constituents of waste liquor are incolloidal form. Colloids of this nature have the property of loweringthe on the fibers.

surface tension of water and result in frothing when air is introduced.However, they cause greatest lowering of the surface tension, and hencemore frothing when the 'pH is that at which the colloids are the leastsoluble. The adjusting of the pH to the point where the optimum amountof froth is formed results in the colloidal material and resins beingprecipitated The precipitated. material results in imparting greaterstrength and water resistance to the finished products. It is believedthat the precipitated material acts as a binder and waterproofing agent.

The best results are obtainable when thefolthe lowing pI-Is areemployed:

. pH Synthetic lumber black liquor 4.0 to 6.0 Kraft black liquor 4.0 to6.0

Sulphite waste liquor 9.0 to 12.0

The process may be carried out at pHs varying from the above, but thebest results and the most economical are obtained within the range aboveindicated.

After the pulp and froth forming materials have been thoroughly aerated,the surplus water may be removed from the formed product by suction,suction and pressure, etc.

If suction is applied to the surface of the formed product'to remove thesurplus moisture the bubbles in the material adjacent that facecollapses, resulting in a denser surface. Thus a dense surface may beformed on one or more of the surfaces of the product.

When using lignocellulose pulp there may be used mechanically,semi-chemically, and chemically produced pulp depending upon the type ofend product desired.

As animal glue is a known colloid, such glue may be employed as thefroth-forming material. When glue is used it is essential that the pH beadjusted to about 4 to 4.5 to obtain a stiff, stable froth. To produce alight colored board of about 4 pounds per cubic foot, 1 part of glue isadded to about 4 parts of light colored produced pulp.

If it is desired that the finished product have a more decorated effect,the froth-fiber mixture is stirred and/or agitated. The finished productwill contain the fibers in a whorly and wavy formation.

The fibers may be proofed by .a process which makes a product notincompatible with the froth-forming material employed. Fireproofing 0fthe fibers may be accomplished by various known methods.

d If greater water resistance is desired, the fibers may be treated byany of the known methods for waterproofing.

A mixture of waste liquors may be used as the frothing agent such as anacid and an alkaline waste liquor,

While there has been specifically described the sion,

preferred embodiment of the invention, it is to be understood that theinvention is not limited to the details described, or sequence of steps,but may be otherwise embodied and practiced within the scope of theclaims. Cognate subject matter not here claimed is claimed in myapplication, Serial No. 263,067, filed March 20, 1939.

What I claim is:

1. A process of producing a vegetable fiber structural unit having adensity of about .75 lb. to about 5 lbs. per cu. ft. which comprisesadding to vegetable fibers in a water suspension alkaline kraftligno-cellulose waste cooking liquor, said waste cooking liquors addedin a ratio to the fibers of 30:1 to 4:1, adding an acid as a frothstabilizer, a colloid insolubilizer, and to adjust the pH of the fibersuspension to within a range of 4 ,to 6, agitating and aerating themixture; forming a structural unit in which the fibers are distended anddrying the unit.

2. A process of manufacturing low density structural units comprisingadding alkaline kraft waste ligno-cellulose cooking liquors to fibers ina water suspension, said waste cooking liquor added in a ratio to thefibers of about 30:1 to about 4:1, adding an acid reacting salt toadjust the pH of the fiber suspension to within the range of 4 to 6, tostabilize froth and insolubilize colloids, agitating and aerating themixture, forming a structural unit from the distended fibers and dryingthe unit without substantially compacting thereof.

3. A process of manufacturing low density structural unit of a densityof .75 to about 5 lbs. per cut. ft., comprising adding to vegetablefibers in a water suspension waste cooking liquor resulting fromalkaline cooking of ligno-cellulose materials, adding an acid to adjustthe pH of the suspension in a range of about 4 to 6 and insolubilize thecolloids of the cooking liquor, I

-of about .75 lb. to about 5 lbs. per cu. ft. comprising adding wastecooking liquors resulting from the alkaline cooking of ligno-cellulosematerials to vegetable fibers in a water suspensaid cooking liquorsadded in a ratio to the fibers of about 30:1 to about 4:1, adding anacid reacting salt to adjust the pH of the suspension to within a rangeof 4 tov 6, to stabilize foam and insolubilize colloids of the wastecooking liquor, agitating and aerating the mixture whereby the fibersare-distended, forming a unit from the distended fiber mass and dryingthe unit at a temperature of about 300 F. to about 350 F. withoutsubstantially consolidation thereof.

JOHN O. BURTON.

